This option is available for the Portal and Shared View extensions and is only supported for Grid views.
To enable this option for your extension, do the following:
Go to the Tables section of your portal or shared view
Click on the table
In the User Actions section, enable the Download records as CSV toggle. If your views are set to use custom view settings (under View Type in each view's settings), change the toggle in the view's User Actions section instead.
Once activated, your users will see a download button just above the grid view:
